The reason that experts are constantly training is that repetition builds fundamentals, and fundamentals are the foundation of good marksmanship. Not having to think about how to line up the sights, reload or clear a malfunction, allow users to be faster at responding to a deadly threat, and can be the difference between winning and losing a fight.
There are also fundamentals for self-defense situations. Recently, Tiger McKee, director of Shootrite Firearms Academy, discussed defensive fundamentals, such as communication, movement and cover. These also have to be practiced in order to be conducted properly when under the stress of an attack. You don’t want your first time using a defensive skill to be during an attack.
If you’re range doesn’t allow this type of training, you can practice using a dummy gun in your home, which also helps you fine tune your home-defense plan with your family.